<!DOCTYPE html>
<html>

<head>
    <meta charset="utf-8">
    <title>菜鸟教程(runoob.com)</title>
    <script>
        function displayDate() {
            document.getElementById("demo").innerHTML = Date();
        }
    </script>
</head>

<body>

    <h1>我的第一个 JavaScript 程序</h1>
    <p id="demo">这是一个段落</p>

    <button type="button" onclick="displayDate()">显示日期</button>

</body>

</html>